I think the argument that gp is trying to make is that it's really hard for git to implement this in a backwards compatible way. You may be right (I don't know anything about Fossil, will take a look!) that Fossil allowed for this by making good design decisions in the past. This is not something that git maintainers can do right now without a time machine though. Old versions are in use out there and will need to keep working if the goal is to make the transition easier for users.